This invention relates generally to an apparatus and method for mixing fuel and an oxidizing agent, such as air. In particular, various embodiments of the present invention relate to a premixer for use in turbo-machinery.
A gas turbine engine is typical of turbo-machinery in which the concept described herein may be employed. It is well known that a gas turbine engine conventionally comprises a compressor for compressing inlet air to an increased pressure for combustion in a combustion chamber. A mixture of fuel and the increased pressure air is burned in the combustion chamber to generate a high temperature gaseous flow stream for causing rotation of turbine blades within the turbine. The turbine blades convert the energy from the high temperature gaseous flow stream into kinetic energy, that is utilized to turn an electrical generator, pump, or other mechanically driven device. Further, the high temperature gaseous flow stream may be used as a heat source to produce steam or provide energy for chemical processing.
Significant reductions in pollutant emissions from gas turbine engines are required to meet increasingly stringent regulatory requirements. Particular interest is focused on reducing nitrogen oxide (NOx) emissions, while preferably maintaining carbon monoxide (CO) and unburned hydrocarbon (UHC) at current or slightly reduced levels. Several approaches exist for lowering NOx emissions, but the generally accepted best practice is to reduce the kinetic formation of NOx by lowering the temperature at which the fuel and air react in the combustor. In a conventional combustor, fuel and air react as they mix within the combustor volume, resulting in extremely high temperatures at the flame front. The lean premixed (LPM) approach reduces reaction temperature by mixing the fuel and air prior to allowing combustion reactions to proceed. If fuel and air are well premixed spatially and temporally prior to combustion, the resulting combustion reactions proceed at a uniform, low temperature which leads to reduced NOx production. Hence a device is required that can consistently provide high levels of premixing between fuel and air, and deliver these reactants to the combustor, preferably in such a way as to ensure stable combustion while preventing flashback of the flame into the premixing section and autoignition of reactants within the premixing chamber.
Thus a need remains for further contributions in the area of premixing technology. The present invention satisfies this need in a novel and nonobvious way.
In one form of the present invention there is an apparatus for mixing fuel with oxidizing agent, comprising a first member and a second member. The first member is substantially hollow and has an inner surface and an outer surface. The surfaces extend between an inlet end and an outlet end of the first member. The inner surface includes a first plurality of substantially radially oriented openings connected to a first passageway receiving a first oxidizing agent. The second member has a first end and a second end and an exterior surface extending therebetween. The exterior surface includes a second plurality of substantially radially oriented openings connected to a second passageway receiving a second oxidizing agent. At least a portion of the exterior surface of the second member is positioned within the first member so that the inner surface of the first member and the exterior surface of the second member define a mixing channel.
In another form of the present invention there is an apparatus for mixing fuel with oxidizing agent, comprising an outer body and an inner body. The outer body has an interior surface that extends between an inlet end and an outlet end. The interior surface of the outer body includes a first plurality of openings. The inner body has an exterior surface that extends between a first end and a second end. The exterior surface of the inner body includes a second plurality of openings. At least a portion of the exterior surface of the inner body is positioned within the outer body to define a mixing channel. The mixing channel being defined by the exterior surface of the inner body and the interior surface of the outer body. The first and second plurality of opening substantially longitudinally span at least one of the inner body and the outer body.
In yet another form of the present invention there is an apparatus for mixing fuel with oxidizing agent, comprising a substantially hollow first body and a second body at least partially positioned within the first body. The first body has an inner surface including a first plurality of openings. The first plurality of openings are spaced around a perimeter of the inner surface at an axial location of the inner surface. The second body has an outer surface including a second plurality of openings, the second plurality of openings are spaced around a perimeter of the outer surface of the second body. The second plurality of openings are offset from the first plurality of openings at the axial location.
In another form of the present invention there is a method of mixing a fuel and an oxidizing agent. The method comprises providing a first body having an inner surface with a first length extending between an inlet end and an outlet end, the inner surface defining a mixing volume. At least a portion of a second body having an outer surface is positioned within the mixing volume, the outer surface of the second body and the inner surface of the first body defining a mixing channel, the outer surface having a second length extending between a first end and a second end. Fuel is injected into the mixing channel at the inlet end. An oxidizing agent such as air is introduced into the mixing channel substantially radially inward from the inner surface of the first body. An oxidizing agent such as air is also introduced into the mixing channel substantially radially outward from the outer surface of the second body. In one refinement of this form of the invention the oxidizing agent introduced substantially radially inwardly is radially offset from that introduced substantially radially outwardly. In another refinement the oxidizing agents are introduced substantially along the entirety of at least one of the lengths of the respective bodies.
One object of the present invention is to provide a unique apparatus and method for mixing a fuel with an oxidizing agent.
Related objects and advantages of the present invention will be apparent from the following description.